The present invention concerns a device for addressing a matrix screen such as a screen of the LCD or plasma type.
The display surfaces of such screens generally have a plurality of subpixels P(i,j) representing one of the primary colours R, G or B and addressed through a crossed network of N horizontal rows and M vertical columns, each subpixel receiving, through a switch which connects it to the adjacent column, during the addressing phase (line time), a sampled video signal.
The spatial resolution of such screens depends on the number and mode of combinations of addressable subpixels used to produce displayable pixels, whose successive sequences constitute the video rows and columns of the image to be displayed.
FIG. 1 illustrates a known mode of combining subpixels, referred to as L mode, use for addressing an orthogonal screen and consisting of producing a displayable pixel by combining three subpixels R, G and B situated on the same row. In this case, the horizontal resolution, denoted Hr, is equal to M/3, and is small compared with the vertical resolution, denoted Hv, whose value is equal to N. This is because the design of a VGA screen of 480 rows and 640 columns using the L combination mode requires a number of columns M equal to 640*3=1920, and a number of rows N equal to 480. In addition, in order to respect the format of the image, this combination mode requires a high number of subpixels, which appreciably increases the cost of the screen.
Moreover, insofar as matrix screens can be addressed only in progressive mode, the combination mode described in FIG. 1 requires the use of an algorithm for adapting the screen to a source of interlaced images.
FIGS. 2 and 3 illustrate respectively a first variant and a second variant of a second known mode of combining subpixels, referred to as Delta mode, used for addressing a screen of the DELTA type. Like the L mode, a displayable pixel is obtained by combining three subpixels R, G and B situated on the same horizontal row. However, in the first variant of the Delta mode, depicted in FIG. 2, two successive rows are offset horizontally with respect to each other by half a subpixel, whilst in the second variant, depicted in FIG. 3, two successive rows are offset horizontally with respect to each other by one and a half subpixels. As a result, in the first case, a column of displayable pixels has a width equal to three and a half times the width of a subpixel whilst in the second case a column of displayable pixels has a width equal to four and a half times that of a subpixel. In the first case, the horizontal resolution is reduced in a proportion of three and a half times with respect to the vertical resolution, whilst in the second case the horizontal resolution is reduced in a proportion of four and a half times with respect to the vertical resolution.